Please Whitelist This Site?
I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)
If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.
If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.
Thanks for your understanding!
Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide
NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.
TCP/IP Address Resolution For IP Version 6
(Page 2 of 2)
Using Solicited-Node Multicast Addresses For Resolution
The solicited-node multicast address
is a special mapping that each device on a multicast-capable network
creates from its unicast address; it
is described in the topic on IPv6 multicast addresses.
The solicited-node address isn't unique for every IPv6 address, but
the odds of any two neighbors on a given network having the same one
are small. Each device that receives a multicasted Neighbor Solicitation
must still check to make sure it is the device whose address the source
is trying to resolve. (This is similar
to how multicast is handled in IPv4, with
32 different IP addresses potentially sharing a multicast MAC address.)
Why bother with this, if devices
still have to check each message? Simple: the multicast will affect
at most a small number of devices. With a broadcast, each and every
device on the local network would receive the message, while the use
of the solicited-node address means at most a couple of devices will
need to process it. Other devices don't even have to bother checking
the Neighbor Solicitation message at all.
Key Concept: Address resolution in IPv6 uses the new Neighbor Discovery (ND) protocol instead of the Address Resolution Protocol. A device trying to send an IPv6 datagram sends a Neighbor Solicitation message to get the address of another device, which responds with a Neighbor Advertisement. When possible, the request is sent using a special type of multicast address rather than broadcast, to improve efficiency.
This is actually a fairly simplified
explanation of how resolution works in IPv6the Neighbor Discovery
protocol is quite complicated. Neighbor solicitations and advertisements
are also used for other functions such as testing reachability of nodes
and determining if duplicate addresses are in use. There are many special
cases and issues that ND addresses to ensure that no problems result
during address resolution. ND also supports proxied address resolution.
Note: Even though I put this topic where it would be near the other discussions of address resolution, the Neighbor Discovery protocol really isn't a layer connection or lower level protocol like ARP. It is analogous to ICMP in its role and function, and in fact makes use of ICMP(v6) messages. One advantage of this architectural change is that there is less dependence on the characteristics of the physical network, so resolution is accomplished in a way more similar to other network support activities. Thus it is possible to make use of facilities that can be applied to all IP datagram transmissions, such as IP security features. The section on ND contains much more information on this subject.
|If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!|
Table Of Contents - Contact Us
The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.